In a phase change ink jet printer for printing an inkjet ink, a feed nip may be used as advancing mechanism for advancing a sheet of paper or any other print substrate in a transport direction over a print area of a print surface. The feed nip is defined by a feed roller and a pressure roller, wherein the feed roller is adapted for driving the sheet. In a typical setup of the phase change ink jet printer the print substrate is intermittently advanced over the print surface in the transport direction, while a carriage moves back and forth across the print substrate in a scanning direction normal to the transport direction and inkjet print heads are energized to eject droplets so as to form the phase change inkjet image on the print substrate in the print area. The phase change ink is solid or in gelled state at room temperature and must be heated above its phase change temperature before droplets of liquid ink can be jetted onto the print substrate.
A print substrate, which is provided from a roll, may be relatively stiff and may have a persistent roll curl directed towards the print surface while being advanced over the print surface. In case a leading edge of the print substrate arrives at the print surface during an advancing step, the leading portion of the print substrate may start bulging from the print surface. A bulging behavior of the print substrate from the print surface may lead to problems of obstructing the carriage or touching the print head.
Several measures can be conceived of in order to suppress the bulging of the print substrate. For example a suction pressure may be provided between the print surface and the print substrate. However especially in case of a bulging print substrate said suction pressure may largely vanish due to pressure leakage towards an edge of the print surface. In another example a stationary flap element extending in the scanning direction may be arranged in contact with said print substrate in order to urge the print substrate towards the print surface. However it has been observed that a contact of the stationary flap element to an outer surface of the print substrate upstream of the print area may lead to disturbance of the crystallization of the phase change ink applied on the print substrate in the print area. This disturbance of the crystallization may lead to the problem of a loss of an image quality of the phase change ink image.